Crane boom suspension



De@ 25 1945 G. Y. ANDERSON CRANE BOOM SUSPENSION 'Y Filed Oct. 2l, 1944 2 Sheets-Sheet 1\ ,w y1N NToR.

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` Dec. v25, 1945. G. Y. ANDERSN l 2,391,440v

CRANE -BOOM SUS PENSION Filed Oct. 21,A 1944 2 Sheets-Sheet 2 INVENTOR.

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Patented Dec. 25, 1945 George Y. Anderson,

to Bucyrus-Erie Company,

.'Milwaukee, Wis., assignerv South` Milwaukee,

Wis., a corporation of Delaware Y Application October 21, 1944, Serial No. 559,778

6 Claims. v (Cl. 212-144) My invention relates to new and useful improvements in crane boom suspensions, and more particularly to such suspensions for low position traveling of mobile cranes, in order to clear overhead obstructions such as bridges, telephone wires,` and the like.

Crane booms are usually pivoted at their foot to the main revolving frame of the crane, which frame carries a fixed A-frame. A boom-suspen sion tackle connects the top or a point near the top of the boom to a sheave orsheaves at the top of the A-frame, and is actuated by a winch on the main frame, for raising and lowering the boom.

'I'he height of the top of the A-frame-on longboom machines prevents attaining low clearance when traveling.

' Accordingly various types of collapsible A- frames have been employed. Or a low A-frame,

and a strut, intermediate the boom have sometimes been employed, as for example in copending application of Trevor O. Davidson, for Suspension for crane booms, Serial No. 510,098, filed November 13, 1943.

But, if this last-mentioned expedient be used to attain very low clearance during traveling,

the following double dilemma is created.

First, if the triangle consisting `of boom, strut, and suspension cable is maintained constant, then either the strut must be too short to be effective when the boom is in erected working position, or the top of theV strut will' still project above the clearance level when the boom is lowered for traveling. Accordingly it is necessary that a fairly long strut be employed, and that the angle between strut and boom be reduced in traveling position.

Secondly, assuming this reduction of angle. If the boom-suspension cable proceeds from the top of thestrut to the extreme outer end of the boom, then when the boom and strut are fully lowered for traveling, the angle between this cable and the boom is so acute as to impose too great a compression load on the boom. -Whereas, if the suspension cable proceeds from the top of the strut to a point on the boom materially short of its outer end,'in order to increase the last abovementioned angle and thereby reduce the compression load on the boom when lowered, then the outer end of the boom is not adequately supported for use as a cr-ane when the boom is erected.

The collapsible A-frames and lowerable struts' the boom in traveling position.

not be strong enough to withstand the compression loads incidental to the use of a low A-frame (orr strut). But, when the A-frame (or strut) is lowered for traveling, this (as already seen) imposes such a compression load on the boom that the boom has to be built strong enough not to haveA needed the high A-frame (or strut) in the rst place. A vicious circle! The principal object of the present invention is to provide a boom suspension which will solve' this dilemma. y f

In addition to my principal object, above stated,I have worked out a number of novel and useful details, which will be readily. evident as the description progresses.

My invention consists in the novel parts and rin the combination and arrangement thereof,

which are defined in the appended claims, and of which one embodiment 'is exemplified in the accompanying drawings, which are hereinafter particularly described and explained.

vThroughout the description, the same reference number is applied to the same member or to similar members. f Figure 1 is a side elevation of my crane, with Figure 2 is a side elevation c the boom blocked-up, preparatory to raismgit.

Infthis ligure, three successive positions of the of the prior art are a -useless anomaly anyway. Y

For the sole need for a high YA-frame (or-strut): is to enable the use of a light boom which would strut,4 just before actual raising starts, are shown.

Figure 3 is a plan view of my crane in traveling position, taken along the line 3-3 of Figure l.

Figure 4 is a side elevation of my crane,l with the boom erected to working position.

Figure 5 is adetailed enlargement, in side elevation, of the connection between one of my suspension lines and my boom.

Figure 6 is van end view of the same, partly in section, taken along the line 6-6 of Figure 5.

Figure '7 shows a variant of the link of Figure 6.

It will be noted that Figures l to 4 are largely conventionalized, inasmuch as structural details form no part of my invention.

Turning now to Figures l and is the main frame of a mobile crane, mounted on creeping traction I2. There is a boom I3, with its foot pivotally supported by the yfront end of the main frame. Pivoted adjacent the foot of the boom is -a strut I4, which carries sheaves I5 at its upper end. l ,i

As shown, both boom and strut are pivoted directly on the main frame, in fact on a common axis. But this is not essential. Either could be pivoted on the other, adjacent that others foot.`

of my crane, with A of the boom l 3, we see that I I Accordingly in my claims I shall employ the generic term pivotally supported by the main frame to describe the pivotal support of each of these two elements.

High up on the upper works I I are sheaves I 6.

. The main frame also carries a boom-hoist winch elements than cables (such, for example, as chainsor rods) could be used in place of cables I9 and 22 or either of them. Accordingly in my claims I shall employ the generic term suspension means to designate each of these cables or equivalent.

Inasmuch as auxiliary cables 22 play no part in the support of the boom when the boom is in traveling position, they may during travel be dis-V posed in any manner convenient to the operator. As shown, they lie loose upon the top of the boom; but they might equally well be then wholly disconnected during travel; or they might then remain connected to the main boom-suspension cables I9, and disconnected from anchorages 23; or, as shown in Figure 7 and hereinafter described, they might remain connected, even during travel.

It will be noted, from Figure 1, what low clearance is attained by my device in traveling position, and yet without a too sharp angle between cable I9 and boom I3,

Turning now to Figure 2, we see that the machine has stopped moving, and that boom I3 is supported on blocking 24.

Strut '14 is now lowered to the lower dotted position shown in Figure 2. This releases the load on cables I9 thus enabling them to be d etached from anchorages 2I, and attached to the ends of cables 22, as shown in full lines in this figure. Strut I4 is then raised to the upper dotted position, thus straightening the combined cables and taking the load off the blocks.

Further raising of strut I4, brings the parts to the operating position shown in Figure 4.

Returning to traveling position is accomplished by reversing the above-described process.

The lengths of cables I9 and 22, with respect to the sizes and positions of the other elements, is important. Thus the length of cables I9 should preferablyv be substantially equal to the distance from the top of strut I4 to the attachment 2l, when both strut and boom are in lowered clearance position. And the combined length of cables I9 and 22 should preferably be slightly longer than the distance from the top of strut I4 to point 23, when both strut and boom are in that same lowered clearance position.

.It should be noted that, in traveling position, as shown in Figure 1 and 3, my invention amounts to temporarily shortening that part of the boom subjected to compression load due t the suspen sion, and thereby increasing the booms ability to withstand compression loads, and at the same time reducing the induced compression by in creasing the angle between the boom and the suspension cables from what this angle would be but for my invention. Also the overhanging portion of the boom is then used to balance-out the bending stress.

Turning now to Figures 5 and 6, let us consider the details of the attachment of cables I9 to .boom I3.

25 is a short boom-section which can be readily interposed between the outer section 2B and the next to outer section 21 of a. standard boom. The three sections can be secured together in any convenient manner, as by bolts or rivets through holes 28.

A tube 29 extending across from side to side of section 25 constitutes an axle for two rope-connections, each of which consists of a piece of plate 30 welded to a hub 3|. All of which constitutes an attaching means on the boom.

Caps 32, held in place on the ends of tube 29, by bolt 33, serve to hold the rope-connections in place.

'1 -here is a guard 34 over each end of tube V29.

Cable I9 ends in a rope-.socket 35. plate piece 30 of the rope connection has a hole 36 for at-, tachment of the rope-socket 35 by means of bolt or pin 31.

When not in use, plate piece 39 can be held out of the way by bolt 38 passing through its hole 36 and through aligned holes in guard 34 and the adjacent structural piece of section 25.

In the variant shown in Figure 7, plate 39 is replaced by a link 39. As before, cable I9 is at. tached to link 39 by rope-socket 35 at hole 36. But nowcable 22 is also attached to link 3 9 by rope-socket 42 at hole 4I. Hole 40 can be slipped over tube 29, but guard 34 must be removed for access thereto.

In this variant, in the erected position (comparable to Figure 4 of the iirst variant), cable I9, link 39 and cable 2 2, together form one con, tinuous complete boom-suspension means.

When link 39 is attached to tube 29 for traveling, cable 22 hangs limp.

When it is desired to detach link 39 from, or to attach link 39 to, tube 29, a man standing on cable 22 near its attachment to the outer end of the boom, with the boom resting on blocking as shown in Figure 2, can draw hole 40 loose on tube 29, or opposite to tube 29, as the case may be. Otherwise both of these operations would be somewhat diiiicult by mere manpower in the case of a large machine.

Having now described and illustrated one form of my invention, and a s ubvariant thereof, I wish it to be understood that my invention is not to be limited to the specic form or arranger ment of parts herein described and shown.

I claim:

l. In a mobile crane the combination of: a main frame; a boom, having its foot pivotally supported by the main frame; a strut, having its foot pivotally supported by the mainl Vframe` adjacent the foot of the boom; means for raising the strut, and supporting it raised; attaching means on the boom, located intermediate the middle andthe Vouter end of the boom; -xedlength boom-suspension means, capable of extending from the top of the strut to the abovementioned attaching means; and auxiliary fixed length boom-suspension means-capable of attachment to the boom-suspension means and to the outer end of the boom, for alternative support of the boom, when the first mentionedv boom suspension means is detached from the attaching means; whereby alternatively to directly support the boom at its outer end when theboom is raised foot pivotally supported by the main frame, ad- A jacent the foot of the boom; means for raising the strut, and supporting it raised; attaching means on the boom, located intermediate the middle and the outer end of the boom; and xed length boom-suspension means, attached adjacent vthe top of the strut, and capable of selective attachment adjacent the outer end of the boom and to the above-mentioned attaching means; whereby alternatively to directly support the boom at its outer end when the boom is raised for operatingand to support the boom at an intermediate point at an appreciable angle when the boom is lowered for overhead clearance in traveling.

3. A mobile crane according to claim 2, further characterized by the fact that the suspension means is in two sections, one of which is attached to the outer end of the boom, and the other of which is attached to the top of the strut and is capable of selective attachment to the first-mentioned section or to the attaching means on-the boom.

4. A mobile crane according to claim 2, further characterized by the fact that the suspension means is in two sections, one of which is attached to the outer end of the boom, and the other of which is attached to the top of the strut and is capable of selective attachment to the first-mentioned section or to the attaching means on the boom, the length of the second section being the distance from the top of the strut to the attaching means when both strut and boom are in lowered clearance position, and the length of the rst section being such that the total length of the suspension means will be slightly greater than the distance from the top of the strut to the outer end of the boom in this position. Y

5. A mobile crane according to claim2, further characterized by the fact that the suspension means includes an element capable`r of attachment to the attaching means on the boom,

and solocated intermediate the ends of the suspension means that the reach of the suspension means from the top of the strut to the attaching means on the boom will support the boom when both strut and boom are in lowered clearance position, the total length of the suspension means being slightly greater than the distance from the top of the strut to the outer end of.

the boom in this position.

6. A mobile crane according to claim 2, further characterized by the fact that the attaching means on the boom constitutes a part of a short section of boom, capable of being inserted between the two outer sections of a standard boom.

GEORGE Y. ANDERSON. 

